Electrical instrument



A g 29, 5 I T. J. SMULSKE 2,520,898

ELECTRICAL INSTRUMENT Original Filed Aug. 13, 1942 INVENTOR.

Theodor J. Smu [ski Patented Aug. 29, 1950 ELECTRICAL INSTRUMENTTheodore J. Smulski, Gary, Ind., assignor to Productivc Inventions,Inc., a corporation of Indiana Original application August 13, 1942,Serial No. 454,674. Divided and this application April 22, 1946, SerialNo. 863,813

Claims. (Cl. 171-95) My invention relates to electrical instruments andmore particularly to electrical indicating My invention is particularlyadapted for use in a remote indicating system having a sendinginstrument provided with bimetallic means which control the transmissionof power in accordance with a variable factor to be indicated, and abimetallic actuated indicating instrument energized by the power sotransmitted. Heretofore the instruments used in such systems have beencompensated for ambient temperatures so that the accuracy thereof hasbeen satisfactory where there was no great difference between theambient temperature at the sending or transmitting instrument and theambient temperature at the receiving or indicating instrument. When suchindicating systems and instruments are used under certain conditionswhere the ambient temperatures at the transmitting and receivingstations are different, certain factors are encountered for whichcorrection or compensation must be made. For example,-if a remoteindicating system of the type mentioned is used on aircraft, the ambienttemperature at the transmitter may be low due to the high altitude, andthe temperature at the receiving instrument may be relatively high dueto th fact that the receiving instrument is mounted in a heated cabin.

When the sending and receiving instruments have bimetallic elements oflike construction, have like heating element therefor, and convertelectricity to heat at equal rates, the dissipation of heat by radiationat the two instruments will be substantially the same if the ambienttemperatures are the same. If, however, there is considerable differencein the ambient temperatures between the two instruments so that theambient temperature at the receiving instrument is higher, the loss ofheat at the receiving instrument is at a rate much greater than the lossof heat at the transmitting instrument. This change in the rate of heatloss must be taken into consideration in order to provide accurateindication.

In certain instances it has been proposed to utilize an indicatinginstrument having bimetallic actuating means to indicate the electricalcondition of the electrical system of a craft into consideration inorder to provide accurate indication. In accordance with my inventionthese corrections are accomplished by providing some means whereby atthe higher ambient temperatures the bimetallic actuating member of thereceiving instrument may provideian indication by multiplying theeffective deflection of the actuating member by a compensating factor orby decreasing the effort required to produce the indication.

In a remote temperature indicator of the wattage integrator type, theelectrical energy converted to heat at the receiver is a function of thetemperature of the sender environment. The ambient temperature of thereceiver will affect the influence of a given sender temperature uponthe receiver unless compensation is provided, because a largerproportion of the electrical energy converted to heat at the receiverwill be lost through radiation at high ambient temperature of thereceiver than at low ambient temperature thereof.

It is an object of my invention to provide an improved indicating systemand apparatus which will be simple to manufacture but which willovercome the above-mentioned disadvantages.

Another object of my invention is to provide an improved indicatinginstrument in which the bimetallic actuating member is required to actagainst less physical resistance at th higher ambient temperatures.

Still another object of my invention is to provide an improvedindicating instrument in which the action of the bimetalalic member isautomatically multiplied by a factor which changes with the ambienttemperature thereby to provide accurate indication.

Other and further objects of my invention will become more readilyapparent by reference to the following specification taken in connectionwith the accompanying drawing wherein:

Figure 1 is a top view of the essential elements of an indicatinginstrument constructed in accordance with the present invention;

Figure 2 is a perspective view of certain of the elements of theindicating instrument so as to illustrate more clearly certainconstructional features thereof;

Figure 3 is a diagrammatic view explanatory of the circuit arrangementsin which an instrument of this type is commonly used;

Figure 3a is a view showing details of a part of the diagram illustratedin Figure 3;

and in such case the heat loss must be taken Figures 4 and 5 arealternative constructional arrangements made in accordance with the present invention; and 1 Figures 6 and 7 show how certain elements of theindicating instruments may be modified in accordance with the presentinvention.

Referring more particularly to Figures 1 and 2 of the drawing, there isshown a cup-shaped housing and base member Ii within which are supportedcertain operating elements of the indicating instrument. A suitable dialmay be supported by the rim or flange of the cup-shaped housing so thatan indicating hand projecting through a suitable opening in the dialwill provide the desired indication. The base of the housing II haspivotally mounted thereon an arm l2 provided with a perforation throughwhich a headed pin or rivet I3 extends so that the arm [2 is pivotallymounted and frictionally secured in position on the base II. The arm I2is provided with a gear sector portion I4 located at a distance from thepivot stud l3 and positioned adjacent an aperture IS in the base II. Byinserting a geared tool from the bottom of the housing ll into theopening I! the gear sector portion 14 of the arm I! may be engaged sothat by rotation of the tool, the-arm 12 may be moved to a predeterminedposition at the time when the instrument is being initially adjusted.Adjacent the outermost end of the arm I2, there is an upstanding portionis to which there is secured a bimetallic member i'l, best seen in theperspective showing in Figure 2. The bimetallic member I1 is formed soas to be of a generally U-shaped configuration having an ambienttemperature compensating leg l8, a heated leg I! and an interconnectingportion 2!. The heated leg I! is provided with an electrical heatingelement 22 which is connected between a pair of conductor studs 23 and24, each of which is secured in the base ll by suitable insulatingwashers 25 and 26. In order to determine what portion of the ambienttemperature compensating leg I8 is to be eiTective for thiscompensation, a portion of this leg may be turned at right anglesthereto as at 21 thus rendering that portion of the leg ineffective. Inorder to prevent the interconnecting portion 2| from having any movementor action it has been found preferable to provide a curved corrugatedconfiguration for the interconnecting portion. Adjacent the end of thebimetallic leg I9 there is a transverse bimetallic portion 28 whichterminates in a hook portion 29. The transverseportion 28 introduces acompensating factor for correcting for the increase in the heat losswhich occurs for a given rate of electrical heating with rise of ambienttemperature.

The indicating instrument is provided with an indicating hand or member3|, the pointer portion of which extends above the dial which is securedto the flange or rim of the cup-shaped housing, the pointer having tworight angled bends therein adjacent the narrow strip 32 to permit thepointer portion to extend above the engaging the hook 29 of thebimetallic actuating member l9 and having the other side of the aperture34 engaging the hook portion 36 of a spring supporting member 37. Theindicating hand 3| therefore is pivotally supported by two knife edgesupports. Y

, The spring support member 31 is connected by a suitable rivet orsuitable fastening means to an upstanding portion 38 of a pivotallymounted arm 28. The pivotally mounted arm 39 is provided with anaperture through which there extends a pivot stud or fastening means 4|which pivotally and frictionally secures the arm 39 to the bottom of thehousing I I. Adjacent the outer end of the arm 39 there is provided agear sector 42 positioned adjacent an aperture 43 in the 'base of thehousing ll so that by means of a geared tool the arm 32 may be moved toa particular position during the initial adjustment of the instrument.

Referring to Figures 3 and 3a. there is shown an electrical circuit inwhich an instrument of the type shown and described in connection withFigures l and 2 maybe used. This circuit includes, as diagrammaticallyshown in Figure 3, an indicating instrument having a spring supportmember 37. an indicating hand 3|, a bimetallic actuating member I! and aheating element 22 therefor, these parts desirably being constructed asshown in Figures 1 and 2. Where the instrument is to be used to show thecondition of an electrical circuit, the heating element 22 is connectedat one terminal thereof to a suitable source of electric potential 44which in turn is connected to ground. The other terminal of theelectrical heating unit is connected to a terminal A which in turn isconnected to the other side of the electrical system or to ground. Ifthe terminal A is connected to ground or to the other side of thecircuit, the indicating instrument operates to show the volta econdition of the power source 44. Since the ambient temperaturecompensated actuating member l9 will be heated to different valuesdepending upon the voltage of source 44 and the ambient temperature ofthe instrument may vary over a relatively wide range, there must beprovided some means for compensating for this difference in the rate ofheat loss. This is accomplished by using the bimetallic portion 28 inthe arrangement shown in Figure 1 or by any of the other arrangementssubsequently to be described.

Where the electrical instrument is to be used to indicate a variablefactor, as in a liquid level gauge, the terminal A is connected to aterminal B which, in turn is connected to an electrical heating element45 which surrounds a bimetallic leg of a transmitter unit 46. Thetransmitter unit 46 is desirably of the same construction as thereceiver unit, comprising a V-shaped bimetallic element having the partsl8, l9, 2| and 28, the spring 31, and a, loop 33 connecting 28 and 37.Adjacent the free end of the bimetallic element there is an electricalcontact 41 which cooperates with a mechanically movable electric contact48 which in turn is connected to ground. If for example, the variablefactor to be indicated is the level of a liquid, there will be provideda suitable float 49 connected to actuate a cam 5| which operates againsta cam follower 52 so as to move the contact 48 to a positioncorresponding to the level of the liquid. Transmitting instrumentsof thetype suitable for use in the circuit of thistype may be any of theinstruments shown in United States Letters Patent No. 2,006,608, grantedJuly 2, 1935 upon the application of T. J. Smulski; Reissue No. 21,527,granted August 6, 1940 upon the application of T. J. Smulski; or PatentNo. 2,133,077, granted October 11, 1938 upon the application of LeonardBoddy. Such transmitting instruments are utilized in an electricalindicating system ingranted October 25, 1932 upon the application of F.M. Slough.

The operation of the electrical circuit shown in Figure 3 may be brieflydescribed by stating that it will be assumed that the liquid levelcauses the adjustable contact 48 to be moved to a particular position.Electrical energy flowing throu h the circuit from the source 44produces heating of the transmitter leg of the ambient temperaturecompensated bimetallic element 48 by means of the electrical heatingelement 48 thereof so that the bimetallic element is warped thus tendingto move the electrical contact 41 away from the contact 48 thereby tobreak the circuit. If the circuit is broken the bimetallic element 46begins to cool so that contact is again established between the contacts41 and 48 and by repetition of this action additional current impulsesare caused to be transmitted to the indicating unit. This making andbreaking of the contacts occurs at a relatively rapid rate and theimpulses of power thus transmitted serve to provide heating of thereceiver leg IQ of the bimetallic actuating member by means of theheating element 22 so that the bimetallic element i! will cause theindicator 8| to assume a. position such that it indicates the conditionof the variable factor at the transmitting unit.

If it is assumed that the indicating instrument used in connection withFigure 3 is of the type shown in Figures 1 and 2, it will be readilyapparent to those skilled in the art that current flowing through theheating element 22 will heat the pointer actuating leg I! of thebimetallic actuating member I! so as to cause this member to move insuch direction as to move the indicating pointer II to a particularposition on the dial. Where the ambient temperatures at both the senderand receiver are the same, the heat losses are the same and accurateindication will be obtained. If the ambient temperature at the receiveris higher than that at the transmitter and the amounts of electricalenergy converted to heat at the receiver and the transmitter are thesame, there will be a greater heat loss at the receiver, thus producinginaccurate indication. At the higher ambient temperature the rate ofheat loss wil be considerably greater than at the lower temperature andhence the heating effect produced by the current flowing through theheating element 22 will not produce as great movement of the indicatingpointer for a given change of the condition to be indicated as would bethe case at a lower ambient temperature of the receiver. Since theindicating pointer 8| is supported by a knife edge mounting whichincludes a mounting spring 8?, any action of the leg I9 is one which isopposed to a certain degree by the bias exerted by the spring mounting31. At the time that the instrument is initially calibrated the biasexerted by the mounting member 31 is controlled by adjustment of.

the position of the leg or arm 88 as determined by the operator by meansof a gear tool inserted in the aperture 43 which engages the gear sector42.. In the arrangement shown in Figure 1, the bimetallic member 28 ispositioned in a generally transverse direction to the direction of thebimetallic leg |8, so that the high ambient temperatures will cause thisportion 28 to move at substantially right angles to the movementof .theleg I! and in a direction toward the mounting spring 31 thereby ineffect reducing the amount of bias against which the actuating leg [8will operate. This reduction of the bias exerted by the spring 31 athigh ambient temperatures permits the mechanical force of the heatedbimetallic leg iii to produce a slightly greater movement of theindicating hand 8| thereby to produce substantially the same extent ofmovement of the pointer for a given change of the factor to beindicated, regardless of the ambient temperature of the receiver.

While. in the arrangements shown in Figures -1 and 2, the mechanicalbias of the spring member 81 has been reduced by a bimetallic portion 28located adjacent the free end of the bimetallic member l8, it ispossible to produce a similar reduction of the mechanical bias by otherarrangements.

' Thus, for example, in Figure 4 there is again shown an indicatinginstrument having a housing Ha provided with a pivoted arm l2a securedby a stud |3a so that the arm Ila may be adjusted by means of a gearsector |4a posisitioned adjacent an aperture Ilia in the bottom of theenclosure lia. The supporting enclosure Ila is also provided withanother arm 88:; which is provided with a gear sector 42:: positionedadjacent an aperture 43a. in the bottom of the supporting frame. The arm38a is provided with an upstanding portion 88a which in turn supportsthe spring support member 31a. The arm |2a is provided with anupstanding por-- tion |6a which in the present instance is atsubstantially right angles to the portion I8 of the corresponding arm I2 in Figure 1. Mounted on the portion |6a of Figure 4 there is abimetallic actuating member which has a bimetallic portion 63, anambient temperature compensated leg 54, a connecting portion 88 and anactuating leg 56 which is provided with a suitable heating element. Theend of the actuating leg 58 is provided directly with a hook portionwhich in turn engages a suitable indicating pointer in a manner similarto that shown in Figure 2. In the present arrangement the ambienttemperature increase produces a warping of the bimetallic portion 88 soas to reduce the amount of mechanical bias exerted upon the actuatingleg 56 and at the same time there is introduced by virtue of itsposition by the bimetallic member 53, a correction factor which changesthe eifective pivot of the actuating hand of the indicating hand 8|.This occurs because the bimetallic portion 58 is positioned at the endof the ambient temperature compensating leg 54. Thus this bimetallicportion 59 produces in effect a sort of rotation of the entirebimetallic actuating assembly comprising the ambient temperaturecompensating leg 8 and the interconnecting portion 88 into actuatingmember 56. It is believed that from this description no furtherexplanation of the operation is necessary as this will be readilyunderstood by those skilled in the art.

Instead of having a bimetallic portion such as 53 in Figure 4 whichsimultaneously reduces the mechanical bias and shifts the pivot of theindicating hand, there may be provided a separate bimetallic element asis shown in Figure 5. Thus in Figure 5 there is provided a housing m;having therein a pivoted member mimvided with an upstanding portion llbwhich in turn supports a bimetallic member 51 to the outer end of whichthere is connected by suitable means a bimetallic actuating assemblycomprising the compensating leg 66, the interconnecting portion 59 andthe heated leg ii. A second pivoted member 39b is provided with anupstanding portion 38b which in turn supports the spring supportingmember 8112. The indicating hand is connected by a hooked end portion ofthe bimetallic leg BI and a hooked end portion of the spring supportingmember 31b. By virtue of the fact that the bimetallic member 51 ispositioned on the other side of the bimetallic actuating assembly, theassembly will move in a direction opposite to the movement or portion 53of Figure 4, the bimetallic member 51 tending to move toward the centerof the housing lib with increase of ambient temperature. This produces arotation of the bimetallic members 58, 59, and 6|, thus'changing theefiective pivot of the indicating hand and also changing the mechanicalbias which is exerted by the spring member 31b.

If desired, compensation for changes of heat losses with change ofambient temperature may be introduced by such arrangements as are shownin Figures 6 and 7. For example, in Figure 6 there is shown an arm 390which is provided with an upstanding portion 36c which in turn supportsa spring member 310 having se-' cured to the outer end thereof abimetallic member 62 which has at its free end a hook portion 83 forengagement with the apertured portion of the indicating hand. In sucharrangement the bimetallic member 62 at increased ambient temperatureswill warp toward the center of the instrument thereby reducing themechanical bias against which the bimetallic actuating member mustoperate without any substantial change in the effective pivot 01 theindicating hand.

Another way of accomplishing substantially the same result as was doneby the arrangee ment shown in Figure 6 may be by the means shown inFigure '7. Figure '7 therefore shows an arm 39d provided with anupstanding portion 38d which in turn supports a spring support member31d. Mounted adjacent to a,portion of the spring member 31d is abimetallic portion 64 which is so positioned that at the high ambienttemperatures the bimetallic Dortions 64 will 'warp toward the center ofthe instrument housing thereby to relieve or reduce the mechanical biaswhich may be exerted by the spring arm 31d upon the indicating handwithout any effective change in the pivot thereof.

While for the purposes of explanation of my invention there have beenshown certain specific embodiments, it is to be understood that I am notto be limited thereto since obviously modifications may be made in theinstrumentalities employed without departing from the spirit and scopeof my invention as set forth in the appended claims.

I claim:

1. An electrical instrument having heat responsive means for actuatingan indicator, said means having a first portion provided with anelectric heating element adapted to be energized in accordance with thecondition to be indicated, a second heat responsive portion operativelyconnected with said first portion for efiecting comcaused by variationsof ambient temperature, and a third heat responsive portion operativelyconnected with said second portion to supplement. 4 the action to beproduced by said heated portion,. and said third portion being arrangedto increase.

in response to ambient temperature rise, the extent of movement of theindicator produced by the heat responsive portions referred to inresponse to a given rise of temperature above the ambient temperaturethereby to compensate for the increase in heat loss of said heatresponsive means at higher ambient temperatures.

2. Indicator means comprising an indicator, a plurality of heatresponsive means and yieldable means, one of said heat responsive meansand said yieldable means being engageable with said indicator, anotherof said heat responsive means operatively connected with said one heatresponsive means and being actable to influence the heat responsivemeans engaging said indicator, and auxiliary heat responsive meansoperatively connected with said another heat responsive means whereby tofurther assist in infiuencing the operation of said indicator.

3. An electrical instrument having means for actuating an indicator,said means including a first bimetallic portion provided with anelectric heating element adapted to be energized in accordance with thecondition to be indicated, a second bimetallic portion connected withthe first portion for effecting compensation of any change which mayoccur in said first portion caused by variations of ambienttemperatures, and a third bimetallic portion operatively connected withsaid second bimetallic portion to supplement the action produceable bysaid heated portion, said third portion being arranged to increase inresponse to ambient temperature rise, the extent of movement of theindicator produced by said first portion in response to a given rise ofa temperature of the first portion above the ambient temperature therebyto compensate for the increase in heat loss of said heated portion athigher ambient temperatures.

4. An electrical indicating instrument comprising, in combination,bimetallic means which includes a bimetallic actuating portion and anambient temperature compensating portion, electric heating means for oneof said portions, an indicating member actuable by said bimetallicactuating portion, means for applying a bias to assist in controllingthe movement of said indicatlng member, and bimetallic means operativelyconnected to said ambient temperature compensating portion andresponsive to ambient temperature to vary said bias as the ambienttemperature changes.

5. An electrical indicating instrument comprising, in combination, abimetallic actuating member which includes an actuating leg and anambient temperature compensating leg, electrical heating means for theactuating leg, an indicating member actuable by said bimetallicactuating leg, means for applying a bias to influence the movement ofsaid actuating leg, and heat responsive means operatively connected tosaid ambient temperature compensating leg and responsive to ambienttemperature to influence the bias as the ambient temperature changes. 7

6. Indicator means comprising a mounting, a generally U-shapedbimetallic member comprised of a pair of portions, one of said portionsbeing engageable with said indicator and constructed and arrangedwhereby the same may be heated pensation for movement of said firstportion by an element adapted to be associated therewith,

another of said portions providing means for effecting compensation formovement of said one' portion caused by variations of ambienttemperature, and heat responsive means operatively connected with saidcompensating portion whereby to assist in influencing the operation ofsaid bimetallic member to control the movement of said indicator, andbiasing means engageable with said indicator and cooperable with saidone portion of said member assisting to maintain said indicator in apredetermined position.

'I. An indicating instrument comprising heat responsive means whichincludes an actuating portion and an ambient temperature compensatingportion, means for heating one of said portions, an indicating memberactuable by said heat responsive means, means for applying a bias toassist in controlling the movement of said indicating member, andadditional heat responsive means operatively connected with said ambienttemperature compensating portion and responsive to ambient temperatureto vary said bias as the ambient temperature changes.

8. An indicating instrument comprising heat responsive means whichincludes an actuating portion and an ambient temperature compensatingportion, means whereby one of said portions may be heated, an indicatingmember actuable by said actuating portion, means for applying a bias toassist in controlling the movement of said indicating member, andadditional heat responsive means operatively connected with saidtemperature compensating portion and responsive to ambient temperatureto vary said bias as the ambient temperature changes.

9. An indicating instrument comprising a heat responsive member whichincludes an actuating leg and an ambient temperature compensating leg,an electrical heating means for one of said legs, an indicating memberactuable by the leg adapted to be heated, means for applying a bias toinfluence the movement of said actuating leg, and heat responsive meansoperatively connected with said temperature compensating leg and re-' toinfluence the movement of said actuating leg,

and heat responsive means operatively connected with said temperaturecompensating leg and responsive to ambient temperature to influence thebias as the ambient temperature changes.

THEODORE J. SMULSKI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATEN'I'S Number Name Date Re. 21,527 Smulski Aug. 6, 19401,885,052 Smulski Oct. 25, 1932 2,006,608 Smulski July 2, 1935 2,022,441Smulski Nov. 26, 1935 2,107,560 Boddy Feb. 8, 1938 2,133,077 Boddy Oct.11, 1938

